The Effect of Disk Warpage/Skew on the Deflection and Vibration of
Flexible
Disk Spinning Above a Baseplate and in Contact With a Point-Head
R.Y. Wu and G.G. Adams
Summary
A flexible disk, with small initial warpage/skew, is spinning in close
proximity to a stationary baseplate. The partial differential equation for the
disk deflection is coupled to the Reynolds equation of the stabilizing
air-film. Disk
warpage/skew produces a small change in the deflection which rotates with the
disk. These deflections are obtained by linearizing the coupled equations
about the axisymmetric configuration corresponding to a perfect disk. Numerical
solutions are obtained and compared for different values of rotational speed
and air-film thickness. The results show that among the three skewed/warped
disks modeled, the skewed disk (i.e. the plane of the disk is skewed with
respect to its axis of rotation) produces the largest deflection change (axial runout). With
the effect of a point-contact head included, the existence of disk warpage/skew
causes the head to produce a spatially-fixed harmonically varying force. The
total disk motion is determined by superposition of the deflection pattern
fixed on the disk and the space-fixed head-induced vibration. The disk pitch
angle variation at the head is obtained and the results are compared for
various values of the rotational speed and air-film thickness.
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